package org.apache.maven.properties.internal;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

import java.util.Locale;
import java.util.Map;
import java.util.Properties;

import org.codehaus.plexus.util.Os;

/**
 * Assists the project builder. <strong>Warning:</strong> This is an internal utility class that is
 * only public for technical reasons, it is not part of the public API. In particular, this class
 * can be changed or deleted without prior notice.
 * 
 * @since 3.0
 * @author Benjamin Bentmann
 */
public class EnvironmentUtils {

  private static Properties envVars;

  /**
   * Adds the environment variables in the form of properties whose keys are prefixed with
   * {@code env.}, e.g. {@code
   * env.PATH}. Unlike native environment variables, properties are always case-sensitive. For the
   * sake of determinism, the environment variable names will be normalized to upper case on
   * platforms with case-insensitive variable lookup.
   * 
   * @param props The properties to add the environment variables to, may be {@code null}.
   */
  public static void addEnvVars(Properties props) {
    if (props != null) {
      if (envVars == null) {
        Properties tmp = new Properties();
        boolean caseSensitive = !Os.isFamily(Os.FAMILY_WINDOWS);
        for (Map.Entry<String, String> entry : System.getenv().entrySet()) {
          String key = "env." + (caseSensitive ? entry.getKey() : entry.getKey().toUpperCase(Locale.ENGLISH));
          tmp.setProperty(key, entry.getValue());
        }
        envVars = tmp;
      }

      props.putAll(envVars);
    }
  }

}
